My mother wants my sister to upstage me at my wedding. The Guardian.

My mother has always put me down in order to make my sister feel good by comparison. No one has been allowed to compliment me in the presence of my mother without her mentioning how the same compliment applies to my sister or praise her in another way.

She denies it and that’s the end of the conversation. I was academically gifted as a child and now work in a respected profession. My sister wasn’t, and doesn’t, but has made a success of her life and career. This reflects my mother’s family and I think she identifies with my sister more and she may be trying to compensate for something she lacked in her own upbringing.

My mother’s behaviour did huge damage. I grew up with no self-esteem or feeling of worth. I could gain praise from my father, but only for good grades. From childhood into my mid-20s I suffered depression, self-harm, suicide attempts and crippling anxiety about exams or being assessed. I dropped out of university before finding a therapist and beginning recovery. I struggle with intimacy in friendships and relationships, as my upbringing taught me I was not lovable.

I am now getting married and otherwise life is going well, but I still resent my mother and find it hard to forgive. My sister naturally enjoys the way my mum behaves and colludes with it. I sink back into depression for a while each time I speak to either of them.

Now she is determined to put my sister in the spotlight at my wedding (insisting I make her a bridesmaid, allow her to make the cake and even announce her own engagement at our reception).

I have stood up for myself and said no, but they are going behind my back. My brother tells me about conversations in which they discuss these plans, but asks me not to confront them as he’ll face the fallout.

I want to cut contact with them both but as this may to lead to estrangement with other family members, I need to be sure. How could I begin to broach this if my mother won’t acknowledge what she does?

I think the way to approach it is to try to forge a relationship with your sister that doesn’t include your mother. For your mother to be part of making things better, she would need to accept responsibility. This seems unlikely.

You have said nothing about your relationship with your sister, when not under the matriarchal shadow, and even highly toxic sibling relationships can improve radically when allowed to stand alone. Although your sister appears to collude, I’d like to know more about how she really feels.

I consulted psychotherapist Eve Ashley (childspsychotherapy.org.uk). “Your mother can’t take in what she’s actually doing,” she says. “It’s as if she’s stuck. And she seems to have a lot of power.”

This power appears to stop anyone standing up to your mother. We don’t know why she acts in this biased way. You may actually be her favourite and in her clumsy way – to hide it – she has swung too far the other way. There may be something in your sister’s upbringing about which she feels guilty. It may be her own upbringing, as you say or, Ashley suggests: “It may be something to do with your mother’s own relationship with her husband.”

There may be something potent at work that, as Ashley points out, “seems to serve a purpose which is currently very strong”.

Remember that you are about to start a new life with someone who will stand up for you, one presumes, in the family dynamic. You are starting to branch out. Trying to take over your wedding in the way your mother proposes – which is absolutely unreasonable – seems to be the final attempt by your mother to suck you back into this unbalanced, unhealthy family dynamic.

I see that you are in a difficult position, having said no to your mother but fearing she will press on regardless. I would enlist the support of your husband and see what he thinks – it’s his wedding too.

Also, talk to your sister. Who knows, she may turn out to be your greatest ally. If you have to go ahead with the wedding with your mother conducting it, I would try to ring-fence her involvement. After all, the guests will be there for you, and make it about you. Beyond that, look forward to the life you will have after your wedding day. You don’t have to cut contact with anyone to start living your own life, but make that contact on your terms from now on.